Question

A 57 year old man undergoes total knee replacement for severe degenerative joint disease. four days after surgery, he develops an acute onset of shortness off breath and right-sided pleuritic chest pain. He is now in moderate respiratory distress with a respiratory rate of 28 breaths per minute, heart rate of 120 bpm, blood pressure of 110/70 mm Hg. Oxygen saturation is 90%. Lung examination is normal. Cardiac examination reveals tachycardia but is otherwise unremarkable. The right lower extremity is post surgical, healing well and 2+ pitting edema, calf tenderness, erythema, an warmth; the left leg is normal. He has a positive Homan sign on the right (calf pain on dorsiflexion).

I am pretty sure this is a diagnosis of PE from a DVT. I have finished the other questions but still have these ones.

1. What changes might you expect in ventilation/perfusion? (is this a high V/Q ratio, that what I think, and why?)
2. Would you expect to see changes in the spirometry readings (tidal volume and FEV1)?

Answer 1

V/Q mismatch will occur because of redirection of blood supply from occluded pulmonary artery to non occluded vasculature. As a result, V/Q will increase in embolised lung area whereas it will be low in non embolised area as there will be high perfusion.

Spirometry is relative contraindication for pulmonary embolism.